Pyrethroid re-evaluation will reach far beyond California

Fair warning American agriculture: When California leads, the nation bleeds.

Golden State regulators are in the beginning stages of the most extensive pesticide re-evaluation in the state’s history. It focuses on widely used pyrethroid pesticides. It will impact the use of the pesticide class — not only in California, but nationwide, where it has been used for more than three decades without any major biological/environmental impact until now.

The California Department of Pesticide Regulations placed 20 synthetic pyrethroids in 608 products from 123 registrants under review, after the active ingredient was discovered in sediments — not the water — of California urban and rural waterways.

It has been detected bound to sediments at levels toxic to a quarter-inch-long crustacean, Hyalella azteca, which is common in aquatic systems, and is used by scientists as an indicator of environmental health and water quality in streams and lakes.

The levels were very high in coastal sediment analysis, according to Parry Klassen, executive director of the Coalition for Urban/Rural Environmental Stewardship (CURES). In one sample, the level of permethrin was 159 times higher than the proposed sediment objective of 1 ppb, Klassen said at the recent Western Plant Health Association (WPHA) regulatory conference in Sacramento.

The re-evaluation, that likely will lead to at least revised labels, includes some of the most commonly used agricultural pesticides: Capture, Brigade, Baythroid, Karate, Warrior, Ammo, Decis, Danitol, Asana, Pounce, Ambush, Scout, and Fury.

That is the bad news. The good news is that it may take five or six years to finish the required testing and come up with any mitigating labeling, according to Jim Wells, former DPR director who is now with Environmental Solutions Group, a Sacramento consulting service.

Wells is the point person on the West Coast for the Pyrethroid Working Group (PWG), a nationwide task force of pyrethroid registrants. PWG was formed eight years ago to track and evaluate pyrethroid use issues.

DPR placed the group of pyrethroids into re-evaluation about a year ago. Pyrethroids are synthetic insecticides. Pyrethrins, which are natural insecticides, are found in Chrysanthemum cinerariaefolium, a perennial plant with a daisy-like appearance. DPR did not include pesticide products containing naturally occurring pyrethrins in this re-evaluation because pyrethrins are known to break down rapidly in the environment.

While registrants agree that residues have been found, Wells said registrants said the relevance of those finds and the problem are not well defined.

“We know a lot about ag use of pyrethroids, but we do not know nearly as much about urban use,” said Wells. There is a wide array of non-agricultural labels.”

It also will be important to determine how the pyrethroids attached themselves to the sediments. Was it normal use or improper use and disposal, Wells questioned. This will be part of the reevaluation study process.

Bill Chase, an entomologist with McLaughlin Gormley King Company, basic manufacturer of pyrethrins, said he was surprised by the biological toxicity findings of a product that has been on the market for more than three decades.

“When we face challenges like this (re-evaluation), we learn a lot more about a product than we already knew. We already know a lot about these products, but we could learn more,” Chase said.

John Sanders, chief of the DPR monitoring branch, told the WPHA conference that the focus of the reevaluation process will be to determine how the compounds move in the sediments, and what the best ways to mitigate this movement are.

Sanders admits the pyrethroid re-evaluation is a “hot button issue.” However, he said it’s “not on any fast track. We want to give registrants plenty of time to get data in.” Sanders estimates it will take two to three years for data from studies to come in.

While the regulators and registrants work through the pyrethroid re-evaluation, agriculture is being proactive in mitigating sediment movement off farms through programs like CURES.

The focus on pyrethroid stewardship is similar to other pesticide stewardship issues; minimizing off-target movement of pesticides through decreasing or eliminating sediment transport, and managing drift through setbacks and buffers between sensitive areas being treated.

Some other CURES management practices to reduce sediment deposition in waterways include:

•Improving irrigation scheduling.

•Using polyacrylamide (PAM) in irrigation water to reduce runoff.

•Creating basins for water and sediment runoff.

•Building tailwater return systems.

•Using low-pressure drip irrigation or micro sprinklers.

•Letting grasses grow in ditches to catch sediments before they get into waterways.

•Circulating drain water through vegetated ditches of field areas.

•Circulating drain water through constructed wetlands.

Klassen said failure to keep pyrethroids out of waterways could result in the loss of products in high-risk areas, creation of mandatory buffers, additional harsh restrictions, and even elimination of the use of these compounds.

It is an issue that will reach far beyond the agricultural fields in California.